Memantine increases cardiovascular but not behavioral effects of cocaine in methadone-maintained humans
ABSTRACT Previous work has suggested that maintenance on the noncompetitive N-methyl-d-aspartate (NMDA) antagonist, memantine, increased the subjective effects of smoked cocaine in experienced cocaine users. To determine whether this phenomenon occurs in opioid-dependent individuals, eight (seven male, one female) methadone-maintained cocaine smokers participated in a 47-day inpatient and outpatient study to assess the effects of memantine on smoked cocaine self-administration, subjective effects, and cardiovascular responses. The participants were maintained on memantine (0 mg and 20 mg daily) for 7-10 days prior to laboratory testing, using a double-blind crossover design. Under each medication condition during inpatient phases, participants smoked a sample dose of cocaine base (0, 12, 25, and 50 mg) once, and were subsequently given five choice opportunities, 14 min apart, to self-administer that dose of cocaine or receive a merchandise voucher (US 5.00 dollars). Each cocaine dose was tested twice under each medication condition, and the order of medication condition and cocaine dose were varied systematically. Memantine maintenance did not alter the subjective or reinforcing effects of cocaine. Several cardiovascular responses, however, including peak and initial diastolic pressures following cocaine, were significantly greater during memantine maintenance, although these elevations were not clinically significant. Taken together, these findings corroborate earlier data suggesting that this dose of memantine will not be helpful in the pharmacotherapy of cocaine abuse.
SourceAvailable from: Heino Stoever
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ABSTRACT: Prior work by our group has shown the feasibility, safety, and validity of a multi-day, multi-dose paradigm of self-regulated cocaine administration in humans. The current work sought to consolidate these methods in a single-day design focused on reducing logistical complexity, decreasing research burden to human subjects, and increasing suitability for medication development designs. METHODS: Eleven experienced cocaine users participated in a 6-hour, single-day design, consisting of one safety/eligibility and three experimental cocaine periods (during which subjects were allowed to self-administer 8, 16, and 32mg/70kg cocaine doses under a fixed-ratio 1:5minute timeout schedule). Changes in cocaine-induced cardiovascular response, self-administration behavior, and subjective effects were assessed. RESULTS: Procedures were well tolerated by participants, and no significant adverse events were noted. Significant (p<0.05), changes in measures of cocaine self-administration (e.g., responses, infusions, interinfusion intervals, consumption, and plasma levels), cardiovascular response (HR), and subjective effects ("high") were observed. In contrast, cocaine-induced increases in other vital signs (e.g., SBP, DBP) and subjective effect measures (e.g., paranoia) did not differ between doses. CONCLUSIONS: These data support the safety, tolerability and validity of our single-day design. Depending on the application, such methods may afford advantages for assessing the self-regulation of cocaine administration behavior in humans (e.g., including medication development designs).Pharmacology Biochemistry and Behavior 08/2012; 103(1):95-101. DOI:10.1016/j.pbb.2012.08.009 · 2.82 Impact Factor
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ABSTRACT: Memantine, a non-competitive NMDA receptor antagonist approved for Alzheimer's disease with a good safety profile, is increasingly being studied in a variety of non-dementia psychiatric disorders. We aimed to critically review relevant literature on the use of the drug in such disorders. We performed a PubMed search of the effects of memantine in animal models of psychiatric disorders and its effects in human studies of specific psychiatric disorders. The bulk of the data relates to the effects of memantine in major depressive disorder and schizophrenia, although more recent studies have provided data on the use of the drug in bipolar disorder as an add-on. Despite interesting preclinical data, results in major depression are not encouraging. Animal studies investigating the possible usefulness of memantine in schizophrenia are controversial; however, interesting findings were obtained in open studies of schizophrenia, but negative placebo-controlled, double-blind studies cast doubt on their validity. The effects of memantine in anxiety disorders have been poorly investigated, but data indicate that the use of the drug in obsessive-compulsive disorder and post-traumatic stress disorder holds promise, while findings relating to generalized anxiety disorder are rather disappointing. Results in eating disorders, catatonia, impulse control disorders (pathological gambling), substance and alcohol abuse/dependence, and attention-deficit hyperactivity disorder are inconclusive. In most psychiatric non-Alzheimer's disease conditions, the clinical data fail to support the usefulness of memantine as monotherapy or add-on treatment However, recent preclinical and clinical findings suggest that add-on memantine may show antimanic and mood-stabilizing effects in treatment-resistant bipolar disorder.CNS Drugs 08/2012; 26(8):663-90. DOI:10.2165/11634390-000000000-00000 · 4.38 Impact Factor